Various auxiliary machines mounted in automobile engines are driven by crankshafts of engines through belts. For example, when an alternator is connected to a crankshaft of the engine such that the alternator rotates in synchronization with the crankshaft, if the number of rotation of the crankshaft is lowered, electric power generation ability is lowered.
Thereupon, there is proposed a pulley unit in which a one-way clutch is incorporated in the pulley of the alternator, and when the number of rotation of the crankshaft is lowered, the rotation of a rotor of the alternator is continued by inertial force thereof so that electric power generation efficiency is enhanced.
In this pulley unit, the one-way clutch is interposed in an annular space between the pulley and the rotor of the alternator, the one-way clutch is switched between a lock state (power transmitting state) and a free state (power transmission cutting state) corresponding to a difference of rotation between the pulley and rotor, so that power is transmitted or cut between the pulley and the rotor.
The present inventor has considered a pulley unit in which rolling bearings are provided on opposite sides of the one-way clutch in an annular space between the pulley and the rotor, axially opposite ends of the annular space are sealed by means of seal rings, and lubricating oil such as grease is held in the annular space.
As the number of electrical components in an automobile is further increased, the alternator is required to enhance the electric power generation ability. On the other hand, the reduction of the size and weight of the alternator disposed around the automobile engine is also required.
Therefore, under present circumstances, it is difficult to secure wide annular space capable of holding sufficient amount of lubricating oil for lubricating raceways of inner and outer rings of the one-way clutch or the rolling bearing when the pulley unit is used in the alternator.
When the space for holding lubricating oil is small, if the lubricating oil moves toward an outer diameter side by rotation centrifugal force caused by relative rotation of the pulley or the rotor, the holding space of the annular space on the outer diameter side is reduced. As a result, lubricating oil is not held and is prone to leak outside through the seal ring, and an amount of lubricating oil is decreased. This results in that an amount of lubricating oil which is repeatedly used in the raceways of the inner and outer rings is increased, and the lubricating oil is prone to be deteriorated.
Accordingly, it is an object of the present invention to provide a pulley unit having an annular space capable of holding lubricating oil for eliminating environment in which the lubricating oil is prone to be deteriorated and for enhancing performance thereof.